The MP - who has not been named - has now made an official complaint to parliamentary authorities.

Mr Thomson is already being investigated by the party over complaints about his conduct in a bar.

A source close to the Aberdeen South MP said it would be "inappropriate" to comment at this time, but he has strongly denied any wrong-doing.

Official complaint

The Daily Record has reported that the MP who made the latest allegations about Mr Thomson has claimed that he experienced unwanted physical contact from the Tory MP in the Strangers' Bar at the House of Commons at the end of last year.

He is said to have now made an official statement to the parliament's sexual harassment hotline, and to have been in contact with Westminster's ­Parliamentary Standards Commission.

The MP was frustrated at what he saw as Mr Thomson's denials about his behaviour.